Rule of thumb in evaluating gear mesh 


A quick guide on gear tooth clearance;



No blood = too loose.

Aircraft Mechanic passes out = too tight.

Moderate bleeding = acceptable clearance.


Note to builders: When turning engine over by gripping flywheel, avoid the 10 and 2 O’clock grip because it puts the right thumb very close to the point where the starter and ring gear mesh. Proper mesh clearance is set with a 1/16″ drill in in a separate operation, thumb is not an accepted substitute for 1/16″ drill.



3 Replies to “Rule of thumb in evaluating gear mesh ”

  1. Was that issue of Sport Aviation OK?

  2. Do that too many more times and your thumb will be an acceptable substitute for a 1/16″ drill. Ouch. No need to replicate that experiment to validate the results.

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